The proposed research represents the first systematic investigation of mint flavorings in smokeless tobacco (SLT) products. Main and interactive effects of pH and mint flavorings (menthol and wintergreen) on nicotine will be identified. A comprehensive sample of commercially available SLT products identified as mint flavored (Aim 1) will quantitatively analyzed for pH and flavoring components. The information will be used to determine ranges of pH and flavoring concentrations to amend a non-flavored research SLT referent product (Aim 2). In a double-blind, within-subject experimental design (Aim 3), experienced SLT users will utilize these amended products in the laboratory to examine the effects of pH and mint flavorings on nicotine absorption. Participants will be randomized to one of two mint groups (menthol or wintergreen) and will engage in 5 experimental sessions: 1) referent product, 2) high pH, low mint, 3) high pH, high mint, 4) low pH, low mint, and 5) low pH, high mint. The main outcome variables will be nicotine exposure, cardiovascular effects and subjective evaluations of the experience and product characteristics. Past studies have relied upon comparisons between commercial products. Although SLT products can be selected on a characteristic of interest (for example, pH), there may be other unknown and confounding additives present. This concern is obviated in the proposed research where a single referent product will be parametrically amended by the addition of flavorings and compounds to change pH. Results from the present study will inform the public health community about the effects of popular flavorings on nicotine exposure and offer a new model to study SLT products to assist those who responsibly guide tobacco regulation through evidenced-based knowledge.